Mass optimisation has negative reference value in 'def add_objective' in 'interface\methods_for_level2.py'

[jexalto]

Hey Aviary team,

I was going over some of the examples, and for the run_battery_mission.py (examples\external_subsystems\battery\run_external_battery_mission_example.py) when we optimise for 'mass' (landing mass) the reference value becomes negative (link added below). The mass is therefore maximised instead of minimised. I'm not sure if this is the intention and I am not understanding something, or that this should perhaps be a positive value?

Joaquin Exalto (Elysian Aircraft Team)

https://github.com/OpenMDAO/Aviary/blob/77c5d7c036b3c36b7dfae33dc65a13168bf7caa4/aviary/interface/methods_for_level2.py#L628